This invention relates to a method and apparatus for demisting a gaseous stream and more particularly to the separation of moisture and solid materials from gaseous streams through the use of a centripetal demister.
The conventional technique for demisting gaseous streams has typically involved the use of filtration. However, moisture collecting on the filter media drastically reduces the life of th filters. Replacement of the these filters, such as High Efficiency Particulate Air (HEPA), is time consuming, expensive and inherently impacts operating schedules and budget. Consequently, means for reducing the degradation of the filter media have been sought such as the use of pre-filters installed upstream of HEPA filters. This has been found to be of limited benefit, typically extending the life of the filter media by only a few days. Also, pre-filters and filter media tend to become clogged from solid materials that may be contained within the gaseous stream.
It is an object of the present invention to provide a demister apparatus for separating moisture and solid materials from a moisture laden gaseous stream by using centripetal force.
It is another object of the present invention to provide an economical centripetal demister apparatus for separating harmful moisture and solid materials from a gaseous stream in order to recover or vent the demisted gas.
It is still a further object of the present invention to provide a demister method and apparatus capable of removing or demisting and removing small size droplets from a gaseous stream.
It is still a further object of the present invention to provide a demister method and apparatus that uses much less liquid than a conventional water scrubber and further that the liquid used in the present invention can be recovered and used again.
It is still a further object of the present invention to provide a demister method and apparatus for removing moisture and environmentally harmful solid material prior to a secondary filtration such as a HEPA filter.
It is still another object of the present invention to provide demister system that is self cleaning and will not plug readily with any solutions, mists, or mists and solids.
Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.
To achieve the foregoing and other objects, a method and apparatus for demisting a gaseous stream is provided. The demister apparatus comprises a housing having at least one gas inlet through which moisture laden gas at a first pressure enters. The housing also contains at least a portion of a rotatable hollow shaft having vanes, stiff bristles or wire brushes, extending radially outward therefrom. The hollow shaft has multiple holes throughout the portion of the shaft that is contained within the housing.
The rotation of the shaft, and vanes attached thereto, creates a centrifugal force that separates the moisture, and any particles contained within the gaseous stream, from the gas. The moisture (fluid) and particles are then collected from the housing through a drain, such as a gravity, or pumped drain.
Upon separation of the moisture and/or particles from the gaseous stream, the demisted gas is then drawn radially inward by centripetal force through the holes in the shaft wall. The centripetal force is provided by maintaining the pressure within the hollow shaft at a lower level than the pressure of the gas at the inlet to the housing. The demisted gas can then be collected or, since the harmful particulates have been removed, simply exhausted into the ambient atmosphere.
In another preferred embodiment of the present invention, a moisturizing system is provided to the gas stream prior to its introduction into the housing. By providing sufficient moisture, particulates within the gas become entrained in the moisture, thereby facilitating the removal of the particulates from the gaseous stream. The water or other fluid can be introduced either in the gas inlet of injected into the hollow shaft core where it is flung radially outward and hence collected as waste.